The detection of chemical and/or biological interaction commonly involves microparticles equipped with a functionalized detection surface. When a solution contacts the detection surface, a target component comprised in the solution forms a chemical and/or biological interaction with a functional group grafted on the detection surface. Such interaction usually leads to the emission of a fluorescent signal indicative of the presence of the target component in the composition either directly if the target component is fluorescently labelled or indirectly if the interaction is revealed with a tertiary fluorescently labelled component.
However, non-specific and specific chemical and/or biological interactions may occur between the functionalized surface and components present in the solution, which are not the target component. For this reason, such detection assay often requires a control experiment to provide a control signal that ensures both the accuracy and the reliability of the results. Indeed, such control experiment typically allows determination of the background noise assimilated in that case to the control signal. As used herein, the term background noise is meant to define any non-specific interactions that occur when the functionalized surface is contacted with the solution comprising the target compound.
With the microparticles such as described in WO 2012/106827, a typical experiment protocol for detecting the target component involves two microparticles equipped with two different detection surfaces to provide two signals: a first microparticle is designed for detecting the specific and non-specific interactions of the targeted component to provide the fluorescent signal, without being able to distinguish both interactions, whereas a control microparticle is designed for detecting exclusively the background noise in order to provide the control signal. Thus, an approximation of the specific chemical and/or biological interaction between the target component and the detection surface can be deduced by a comparison of the fluorescent signal and the control signal.
Such experiment protocol is usable in order to analyse a solution with a homogeneous composition meaning that each microparticle is contacted with a predetermined and uniform environment. However, when the composition to be analysed is flowing in a microchannel comprising the microparticles, for example as described in WO 2010/072011, the protocol described above lacks of reproducibility. Indeed, when it comes to compare the signals emitted by two microparticles positioned in two different sections of said microchannel, each microparticle sees a different environment, especially when the concentration of target component is low and varies along and/or across the microchannel.
The present invention aims to remedy all or part of the disadvantages mentioned above.